1. Field of the Invention
This invention relates generally to converter circuits. In particular, this invention relates to a digital to analog converter circuit for converting a plurality of data bytes to corresponding analog signals at very high conversion rates.
2. Description of the Prior Art
Digital to analog converters of the general type provided for by the present invention are essential components of any system wherein digital signals are utilized to control the operation of various electrical and mechanical devices. In a particular situation, for example, the present invention may be utilized in combination with a computer image generator for translating the digital signals produced thereby into analog signals, which are then supplied to a image display apparatus. The image display apparatus, in turn, broadcast upon a reflective display screen a visual image to be observed by a trainee pilot.
Several types of electronic digital to analog converters have been utilized in prior systems. In one type of converter the entire range of digital signals and corresponding analog equivalents are continuously produced and compared with the digital signal to be converted. When the digital signal is found which corresponds to the digital signal to be converted, the corresponding analog signal is gated to an output circuit for utilization thereby.
In another type of digital to analog converter the number to be converted is initially entered into a register comprising a plurality of flip-flops, one for each digit of the number. The flip-flops are utilized to control a decoding network which produces an analog output signal corresponding to the setting of the register.
While performing satisfactorily for their intended purpose of converting digital signals to the corresponding analog equivalents, the aforementioned devices of the prior art ordinarily leave something to be desired, especially from the standpoints of accuracy, complexity of design, and conversion efficiency. In particular, the aformentioned devices of the prior art convert digital signals to their corresponding analog equivalents at rates which are too slow to allow their utilization within visual image generation systems such as that illustrated in a United States Patent Application entitled Pilot Helmet Mounted GIG Display with Eye Coupled Area of Interest, Ser. No. 104,521, by James F. Harvey, Walter S. Chambers, and John J. Kulik.